Thorium

Thorium is a dark grey, radioactive metal of which the principal source is the ore, monazite, a complex phosphate of thorium, uranium, cerium and lanthanides. The metal is soft and ductile and is extracted by precipitation as the hydroxide, along with cerium and uranium; separation is achieved by further extraction with tributyl phosphate from an acid solution. The metal is made by calcium reduction of the oxide or fluoride, and pure thorium can be obtained by decomposing ThI4 on a hot filament (the Van Arkel process). Thorium is used as an alternative reactor fuel to uranium, thorium being converted readily into uranium in the reactor. Thorium is extremely efficient as an energy source, the earthly reserves of thorium containing more energy than all other fossil fuel sources combined.


Symbol
Th

Discovered
1829 by J.J. Berzelius in Stockholm.

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Atomic number 90 Clip
Atomic / Molecular Weight 232.038 gmol-1Clip
Density 11725 kgm-3Clip
Crystal Structure fcc / bcc at 1673K Clip
Lattice constant 508 fmClip
Melting Point 1973 KClip
Boiling Point 4773 KClip
Specific heat capacity 113 Jkg-1K-1Clip
Thermal conductivity 54 Wm-1K-1Clip
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See also: Berzelius, Jons Jakobs, Periodic Table.

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Subjects: Chemistry